Over the years, different types of drain stoppers have been developed in the prior art. For example, drain stoppers having a complicated lever action, wherein the lever which opens and closes the drain stopper is located in close proximity to the spout of the bathtub, are well known in the prior art. However, such drain stoppers have serious drawbacks in that the stopper is removable from the linkage mechanism of the lever, thereby encouraging vandalism in hotel bathrooms and other settings having public access, and also, the linkage mechanism from the lever to the stopper often breaks and is complicated and expensive to manufacture.
In order to overcome the drawbacks associated with such lever drain stoppers, various prior art drain stoppers have been developed which do not require a lever and which may be open and closed by applying pressure to the stopper so that in response to either rubber or spring biasing, the drain stopper pops up to open or compresses to close. The disadvantage of such prior art drain stoppers is that the springs often wear with use and create an ineffective seal. Furthermore, such prior art drain stoppers require complicated cam-shaped parts having interlocking mechanisms which may eventually wear and malfunction and are expensive to machine and manufacture. Other prior art stoppers are of the lift and turn type which are confusing because the direction of turning is not obvious. Also they require components that are costly to manufacture.
Most non-lever operated stoppers that are wholly contained within the drain of a tub are prone to theft since they may be readily removed from the drain. Various attempts have been made to deter theft and vandalism of drain stoppers. U.S. Pat. No. 4,369,531 issued to Swanson discloses a drain stopper having a spring biased plunger. This stopper assembly is secured to the drain body (sometimes referred to in the plumbing fixture industry as a drain plug or spud) such that it cannot be removed from the body without removing the body from the tub. While the stopper disclosed by Swanson is thus inherently vandal resistant, it is difficult to service or replace.
A tamper resistant push-pull type of stopper is disclosed in U.S. Pat. No. 4,720,877 issued to Watts. In order to remove this stopper from a drain on which it is installed, a knob portion of the stopper must first be removed to provide access to a central post which secures the stopper assembly to the drain plug.